This invention relates to photoluminescent chemical markers for tagging liquids or solids. More specifically, this invention relates to fluorene copolymer markers.
There is a strong drive for manufacturers and taxing authorities to tag various solid or liquid products with silent markers. Silent markers are invisible to the naked eye and yet identify the product when simple testing procedures are used. These silent markers when used in liquids are miscible with the liquid to be tagged, are visually undetectable, should not affect the use and performance of the product and should be difficult to remove (e.g. by extraction, filtration, bleaching, reactive conversion). These markers must be easily identifiable by sampling and testing the product and, in some cases, quantifiable by the user.
These markers are commonly used to tag petroleum fuels in order to confirm grade quality and taxation status. Markers are required by government regulation in order to police the tax classification of interchangeable fuels such as diesel fuel, farm equipment fuel and heating oil. Markers are also useful for locating the origin of leaks in storage tanks, lubrication systems, liquid handling facilities, etc.
However, there is an increasing trend towards the use of markers in other liquid products including for example beverages such as soft drinks and alcohols, foodstuffs, paints, cosmetics, refrigerants, lubricants, pharmaceuticals, waxes, varnishes, solvents, polymers, bulk chemicals and rubbers. For example, name brand manufacturers of liquid products or those using inks to print brand name labels will wish to tag products to confirm grade quality throughout their distribution systems and to confirm origin of the product.
Furthermore, markers can also be introduced in solid during processing, in melts, castings or solid mixtures, or by coating or impregnating the solid with the marker. For example, electronic products could be marked by coating their outer or inner surfaces. As a further example, markers, which are solid at room temperature can be designed to melt at temperatures used for melting and molding plastics so that the marker can be processed with the melt. Another possibility is to provide the marker in a solution, introduce the solution in a melt or resin and evaporate the solvent so as to re-solidify the marker within the targeted product.
Thus, in general, markers will commonly be used to identify origin or grade of a given product. Silent markers will ideally be hard to remove or copy so as to foil attempts to remove or mimic the markers.
Although a number of photoluminescent markers are known, a main drawback is their lack of sensitivity at low concentrations. Prior art markers are usually deployed in liquids to be tagged in concentrations in the range of 1 to 100 ppm (parts per million, volume per volume). These concentrations are often high enough to negatively affect physical or chemical properties of the product to be tagged. For example, in the case of petroleum fuels, too much of a marker can cause engine malfunctions and deposits.
Thus, there is a need for highly sensitive markers capable of effectively tagging solids or liquids at concentrations in the range of ppb (parts per billion), which may be readily identified and preferably even quantified. From a cost standpoint, it is also preferable to use less of the chemical marker.
Another drawback of current chemical photoluminescent markers is a limited range of available solubility in different organic and inorganic liquids and a limited range of detectable photoluminescent responses.
Thus, there is a need for markers capable of solubilizing in many different liquids. There is also a need for markers capable or being easily designed so as to provide an extended range of detectable photoluminescent responses.
Yet another drawback is the need for many of the existing silent markers to be extracted by a wet chemical process. Typically, the chemical process includes shaking a sample of the product with a water-based reagent such as described in U.S. Pat. Nos. 4,209,302, 4,735,631, 5,205,840 and 5,902,750. The addition of a chemical agent to the water phase causes the extract to turn to a visibly distinct color. The depth of the color indicates the quantity of marker present in the sample. A laboratory measurement in a spectrometer indicates the concentration of marker present in the isolated sample. Comparing the measured concentration with the original concentration of marker in the fuel assists in the identification of the fuel, However, such technique involves disposal problems for the spent sample and is generally burdensome because of the various steps that have to be performed.
Also, some silent markers are large organic molecules that either absorb or fluoresce in the near infrared to mark their presence in a fuel sample. U.S. Pat. Nos. 5,498,808, 5,980,593 and 5,525,516, incorporated herein by reference. In U.S. Pat. Nos. 5,498,808 and 5,980,593, the presence of such silent marker is detected by firstly extracting the marker with an aqueous reagent and then exposing the extract to UV light to witness fluorescence. However, such multi-step procedure is generally burdensome. In U.S. Pat. No. 5,525,516 (squaraines, phthalocyanines and naphthalocyanines markers) and U.S. Pat. No. 5,984,983 (carbonyl markers) the presence of a silent marker is detected by exposing the marker to near infrared radiation and then detecting emitted fluorescent light via a near infrared light detection element. Although meritorious, these efforts have not lead to silent markers being sufficiently sensitive and versatile to properly function in various organic environments. Solubility problems, detection problems and stability problems are often encountered.
Therefore, there remains a great need for a novel class of silent markers which do not require extraction before testing, which fluoresce under simple testing conditions and at very low concentrations, which are soluble and non-reactive in a host of chosen liquids, preferably organic liquids, and which remain sufficiently stable over time whilst present in the organic liquid.
Preferably, the silent marker will be colorless or very lightly colored (will not fluorescence under normal lighting conditions). Also, the silent marker would preferably be essentially insoluble in aqueous media (i.e. less than about 0.2 per 100 ml at 20xc2x0 C.) so as to make its removal via extraction difficult. Still preferably, the marker should be combustible when used to tag combustible fuels.
The invention is next described in connection with certain embodiments; however, it will be clear to those skilled in the art of petroleum product marking that various modifications, additions and subtractions can be made to the described embodiments without departing from the spirit or scope of the invention.
The invention provides fluorene-containing photoluminescent markers for identification purposes and methods for detection of such photoluminescent markers when present in organic liquid products or present in solid products. These novel markers are described in more detail with reference to preferred embodiments.